All About Spines
Dave Tutelman -- January 30, 2008
Back in February 2006, John Kaufman (the head guy at Club Scout,
frequency meter company) asked on the SpineTalker's
things are so slow I have a simple question to ask. What are you trying
to accomplish by spine aligning a shaft? Or maybe I should say trying
to prevent? From all the talk I've heard over the years maybe this
question isn't as trivial as it sounds.
Shaft spines are interesting because there
is evidence that
"aligning the spine" can affect the feel and/or performance of the golf
club. Aligning the spine means rotating the shaft in the hosel, while
building the club, so that the spine of the shaft points in some
specific direction. For instance, the
spine can be placed in the heel-toe plane of the club. Obviously, this
has to be done at the time the shaft is installed in the clubhead.
The next day after John posted his query, there were a few
responses along the lines of "we are trying
to optimise the performance of a golf shaft within the rules of golf".
That caused John to elaborate a bit:
guess my simple question was too brief. You have stated all the results
we hope to acheive by aligning shafts. But what causes these things to
happen when you align a shaft?
John is right that the question is very non-trivial.
I posted my initial thoughts in the form of an outline within about a
month, but it took almost two years before I was ready to write it up
as an article. Here it is.
Be forewarned, this is not the usual clubfitter's view of spines. It is
spines as viewed by an engineer, so intuition and hand-waving are going
to take a back seat. And, unfortunately, too much of what is "generally
known" about spines falls under the heading of intuition and
hand-waving. I'll try to point out where my views deviate from the
"common wisdom", but I may not have done it everywhere.
of all the fallacies and misinformation about spines, among both the
public and custom clubmakers, I'm going to start at the beginning and
work my way from there to John's question.
First, if all you want is advice on how to measure and align spines,
here is a summary of the results. If you want to know why these are the
results, you will have to read further than this summary.
Now for a list of the points in the article, a sort of table of contents. Each consists of a
link to the place in the article where the point is elaborated.
- Don't use bearing-based spine finders to locate the spine; they give wrong answers. Use FLO (Flat Line Oscillation) instead.
The high-frequency FLO plane is the pair of spines (separated by 180*);
the low-frequency FLO plane is the pair of NBPs (again, separated by
180*). The spine plane and the NBP plane are separated by 90*.
Corollary: if your instrument tells you that the spine is 180* from the
NBP (instead of the proper 90*), throw away the procedure or the
instrument that tells you that. It is giving you wrong answers.
Measure the frequency difference between the FLO planes. If it's less
than 3cpm, spine alignment is not going to do anything for performance
or feel (though it may give you some peace of mind).
There is no provable best direction for aligning the spine. Theories
differ, and the experimental evidence is not conclusive. But most
experiments and practice say to place the spine in the heel-toe plane
and the NBP in the target plane. The most likely theories also support
- If you want to ask whether to place the NBP toward
the target or away from it, you weren't paying attention. Go back and
read the points a-e again. The question makes no sense if you accept
Basic definitions and physics
Finding and measuring spine
Both analysis and experimental
evidence are presented to support this
Finally we get to John's question: what are we doing to or for
performance when we align the shaft in the club?
- You should
align so that the direction the shaft 'wants' to bend is in the target
impact. This sounds nice and intuitive, but is
offered with a sound physical rationale -- and I could not find any. Not viable.
the NBP in the target plane allows the hands to square the clubface at
This is plausible, based on the assumption that the shaft bend is in
the target plane in
the vicinity of impact. Unfortunately for the theory, the shaft bend is
not in the target plane during the tens of milliseconds before impact. Not viable.
the shaft bends during the downswing, any bend not in the spine plane
or NBP plane produces forces that tend to move the clubhead out of the
swing plane. This is definitely a true
here -- so far unanswered -- is whether those forces are large enough
to produce the observed results of misalignment. Possibly viable.
the shaft bend at impact is in the vicinity of the clubhead's center of
gravity (CG), align the NBP with the CG -- using the same rationale as
#2 above. This theory suffers from an assumption
to fact. The shaft bend at impact is not in the direction of the CG. Not viable.
advantage is in feel at and after impact, where the clubhead "rebound"
from the ball is in the target plane.
This is consistent with experimental results based on feel. It is not
as clear in explaining experimental results reporting performance
consistent alignment strategy results in a consistent set of clubs, and
that is the best we can expect to do. This does
explain why experiments tend to show that certain alignment positions
seem to be better than others. Not viable.
Some things that don't fit neatly into the other categories:
don't know nearly as much about spine alignment as most clubmakers
would have you believe. And much of what we "know" may not be true. In
fact, some of it is demonstrably false.
Last modified -- 10/12/2008